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authorTom Zanussi <tzanussi@gmail.com>2009-03-22 04:31:04 -0400
committerIngo Molnar <mingo@elte.hu>2009-03-22 13:38:46 -0400
commit7ce7e4249921d5073e764f7ff7ad83cfa9894bd7 (patch)
treed8a3026e85d3230ce39ca99f446abe76a710c337 /kernel/trace/trace_events.c
parent2d622719f1572ef31e0616444a515eba3094d050 (diff)
tracing: add per-event filtering
This patch adds per-event filtering to the event tracing subsystem. It adds a 'filter' debugfs file to each event directory. This file can be written to to set filters; reading from it will display the current set of filters set for that event. Basically, any field listed in the 'format' file for an event can be filtered on (including strings, but not yet other array types) using either matching ('==') or non-matching ('!=') 'predicates'. A 'predicate' can be either a single expression: # echo pid != 0 > filter # cat filter pid != 0 or a compound expression of up to 8 sub-expressions combined using '&&' or '||': # echo comm == Xorg > filter # echo "&& sig != 29" > filter # cat filter comm == Xorg && sig != 29 Only events having field values matching an expression will be available in the trace output; non-matching events are discarded. Note that a compound expression is built up by echoing each sub-expression separately - it's not the most efficient way to do things, but it keeps the parser simple and assumes that compound expressions will be relatively uncommon. In any case, a subsequent patch introducing a way to set filters for entire subsystems should mitigate any need to do this for lots of events. Setting a filter without an '&&' or '||' clears the previous filter completely and sets the filter to the new expression: # cat filter comm == Xorg && sig != 29 # echo comm != Xorg # cat filter comm != Xorg To clear a filter, echo 0 to the filter file: # echo 0 > filter # cat filter none The limit of 8 predicates for a compound expression is arbitrary - for efficiency, it's implemented as an array of pointers to predicates, and 8 seemed more than enough for any filter... Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <1237710665.7703.48.camel@charm-linux> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/trace/trace_events.c')
-rw-r--r--kernel/trace/trace_events.c77
1 files changed, 77 insertions, 0 deletions
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 961b057da28b..97470c48956e 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -459,6 +459,71 @@ event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
459 return r; 459 return r;
460} 460}
461 461
462static ssize_t
463event_filter_read(struct file *filp, char __user *ubuf, size_t cnt,
464 loff_t *ppos)
465{
466 struct ftrace_event_call *call = filp->private_data;
467 struct trace_seq *s;
468 int r;
469
470 if (*ppos)
471 return 0;
472
473 s = kmalloc(sizeof(*s), GFP_KERNEL);
474 if (!s)
475 return -ENOMEM;
476
477 trace_seq_init(s);
478
479 r = filter_print_preds(call->preds, s->buffer);
480 r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, r);
481
482 kfree(s);
483
484 return r;
485}
486
487static ssize_t
488event_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
489 loff_t *ppos)
490{
491 struct ftrace_event_call *call = filp->private_data;
492 char buf[64], *pbuf = buf;
493 struct filter_pred *pred;
494 int err;
495
496 if (cnt >= sizeof(buf))
497 return -EINVAL;
498
499 if (copy_from_user(&buf, ubuf, cnt))
500 return -EFAULT;
501
502 pred = kzalloc(sizeof(*pred), GFP_KERNEL);
503 if (!pred)
504 return -ENOMEM;
505
506 err = filter_parse(&pbuf, pred);
507 if (err < 0) {
508 filter_free_pred(pred);
509 return err;
510 }
511
512 if (pred->clear) {
513 filter_free_preds(call);
514 return cnt;
515 }
516
517 if (filter_add_pred(call, pred)) {
518 filter_free_pred(pred);
519 return -EINVAL;
520 }
521
522 *ppos += cnt;
523
524 return cnt;
525}
526
462static const struct seq_operations show_event_seq_ops = { 527static const struct seq_operations show_event_seq_ops = {
463 .start = t_start, 528 .start = t_start,
464 .next = t_next, 529 .next = t_next,
@@ -504,6 +569,12 @@ static const struct file_operations ftrace_event_id_fops = {
504 .read = event_id_read, 569 .read = event_id_read,
505}; 570};
506 571
572static const struct file_operations ftrace_event_filter_fops = {
573 .open = tracing_open_generic,
574 .read = event_filter_read,
575 .write = event_filter_write,
576};
577
507static struct dentry *event_trace_events_dir(void) 578static struct dentry *event_trace_events_dir(void)
508{ 579{
509 static struct dentry *d_tracer; 580 static struct dentry *d_tracer;
@@ -619,6 +690,12 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
619 } 690 }
620 } 691 }
621 692
693 entry = debugfs_create_file("filter", 0444, call->dir, call,
694 &ftrace_event_filter_fops);
695 if (!entry)
696 pr_warning("Could not create debugfs "
697 "'%s/filter' entry\n", call->name);
698
622 /* A trace may not want to export its format */ 699 /* A trace may not want to export its format */
623 if (!call->show_format) 700 if (!call->show_format)
624 return 0; 701 return 0;